Currently, new types of input interfaces such as a virtual keyboard, a surface computer, and a multi-touching sensing, have been developed. Along with the development of such input interfaces, a user interface which projects a screen, via a projector, where the input interface is made available and enables a user to operate a computing performance on the screen has been being developed.
When such a user interface is implemented through a portable terminal, users may project each user interface screen via a user's portable terminal, and thereby may conveniently exchange information at any time and place. Accordingly, the development of a new technology which may embody information exchange among users via the user interface screen is needed.